Ventilation of dynamoelectric machines



Feb. 17, 1948. MUELLER 2,436,322

VENTILATION OF DYNAMOELECTRIC MACHINES Filed Nov. 10, 1944 2 Sheets-Sheet 1 E ,Ze z 7 l I I o o .32 /s e a 0 35 37 34 K0 7 4 23 22 a 2 4 17 L ZZ7 WETNESSES: lNVENTOR ATTORNEY E. 0. MUELLER VENTILATION OF DYNAMOELECTRIC MACHINES Filed Nov. 10, 194 2 Sheets-Sheet WITNESSES:

ATTORNEY Patented Feb. 17, 1948 VENTILATION OF DYNAMOELECTRIC MACHINES Erich 0. Mueller, Irwin, Pa., assignor to Westinghouse Electric Corporation,

East Pittsburgh,

Pa., a corporation of Pennsylvania Application November 10, 1944, Serial No. 562,783

9 Claims. 1

The present invention relates to the ventilation of dynamo-electric machines and, more particularly, to the ventilation of electric railway motors of the commutator type.

The invention is especially adapted for the ventilation of electric motors such as the singlephase alternating current commutator motors used on electric locomotives, although it obviously could also be used in other types of commutator machines. Railway motors are mounted on the trucks of the locomotive or car, so that the physical size of such motors is subject to rigid limitations, as determined by the dimensions of the trucks, but such motors are required to develop relatively high horsepower output, which means high motor speeds and heavy currents in the motor. The increasin demand for motors of larger and larger output without any increase in size results in the necessity of designing these motors for higher and higher currents, which involves increasing dihiculty in providing adequate cooling. Since the axial length of the commutator in commutator type railway motors is limited, the high currents involved result in relatively high current density in the commutator, and the large amount of heat generated, together with the relatively large number of large brushholders which surround the commutator, create a diflicult problem of coolin the brushholders and commutator.

In the usual method of ventilation which has been used heretofore for railway motors, ventilating air is supplied to the motor through a duct from a blower on the locomotive. The duct is connected to an air inlet opening in the top of the motor frame directly over the commutator, and the air is intended to flow circumferentially around the commutator and then into the ventilating passages in the stator and rotormembers of the motor, escaping through discharge openings at the opposlte, or pinion, end of the motor. The heavy currents involved in these motors require the use of a relatively large number of brushholders spaced around the commutator, and these brushholders impede the circumferential flow of ventilating air, since in effect they divide the space around the commutator into a number of chambers, and obstruct the flow of air from one chamber to the next, forcing the air to flow away from the commutator surface, where it is needed, toward the rocker rings at the ends of the brushholders, and the frame, where no great amount of cooling air is needed.

The air in the spaces between the brushholders, therefore, does not flow freely around the commutator so that there are pockets of hot air adjacent the commutator surface in these spaces, especially at the lower side of the commutator, or the side opposite the air inlet. These hot air pockets cause relatively high commutator and brush temperatures which are very detrimental to successful operation, This inadequate air circulation is especially undesirable when the motor is being started under a heavy load when the current is at a maximum and there is no natural ventilation as the armature is just beginning to rotate. Insuflicient ventilation permits the brushes and brushholders, and the commutator bars themselves, to become extremely hot in a very short time, and burned and loose commutator bars may result. Thus, the inadequate circulation of air obtained with the conventional ventilating systems for commutator type railway motors of high horsepower output results in excessive commutator and brush temperatures, and often leads to failure of the commutator after a relatively short period of service.

Another difliculty which is sometimes encountered is excessive heating of the commutator bar necks to which the connections to the rotor windings are soldered. These soldered connections sometimes become hot enough in service to soften the solder and cause the connections to loosen, resulting in open circuits, because the commutator bar necks are not adequately cooled. Thus, the existing method of cooling railway motors of the commutator type has become inadequate for present and future needs, and better ventilating means must be provided in order to permit high horsepower ratings of these motors without increasing the physical size.

The principal object of the present invention is to provide an improved ventilating system for commutator type electric motors of high horsepower rating.

Another object of the invention is to provide a ventilating system for commutator type electric motors which is so designed that the ventilating air strikes the commutator surface and brushholders at high velocity, and in which hot air pockets in the spaces between the brushholders are eliminated, and very effective circulation of the air is obtained.

A further object of the invention is to provide a ventilating system for commutator type motors in which the ventilating air flows over the commutator and the brushholders and then into passages in the stator and rotor members, and in which substantially all of the air flowing from the commutator into the stator air passages on at least one side of the machine is forced to flow the spaces between the brushholders all the way around the commutator, so as to provide the most efiective cooling of the commutator and brush holders and to prevent the existence of pockets of hot air between the brushholders.

This result might be accomplished by connecting the air duct which supplies ventilating air. to

the motor to an air shield on. the end of the.

motor, and directing the air from the air shield into the spaces between the brushholders. Such. an arrangement, however, would not be suitable because the air shield would have to carry all or" the ventilating air required for. the motor and would necessarily be rather large. There i only a limited space available between the end of the motor and the adjacent wheel, of the locomotive, however, and in order to accommodate an air shield of the required size in this space, it would be necessary to shorten the motor. itself. This, of course, would aggravate the heating problem resulting from the heavy currents, o that no real improvement could-be obtained in this way. With such an arrangement, it would also be necessary to locate the air. duct very close to the locomotive wheels, and in a position where it would interfere with the supports for the body of the locomotive,

In accordance with the present invention, the air duct may be located in the usual position, and it is connected to an air inlet opening in the motor frame directlyover. the commutator. Part of the air flowing through the duct is directed. in a plurality of: generally radial streams into the spaces between the brushholders on the side of the commutatorv adjacent theair inlet, and this. air fiows from the commutator into ventilating passages in boththerotor and stator members. Anothenpart of, the air from the duct flows into an. air shield at the. end of the motor and flows to the opposite side of the motor, where.

it is directed in aplurality of generally axial streams into the spaces between the brushholders on the side of theicommutator. opposite to the.

air inlet. Since the. air. shield has to carry only about one-half of. the ventilating air for the motor, it can be made smallenough to fit into the available spacebetween theend of the motor and the adjacent'wheel' without. requiring any decrease in the sizeof themotor, and a method of cooling is thus provided which is'much more effective than the usual methods which have been used heretofore.

The invention willT be. more fully understood from the followingdetailed description, taken in connection with the accompanying drawings, in which;

Figure 1 is a longitudinal sectionalview of a motor embodying the invention; and

Figs. 2 and 3 are transverse sectional views on the lines II-II and of Fig. 1, respectively.

The invention is shown in the drawings as embodied in an. electric railway. motor having a frame I in which issupported a.laminated stator core 2. The core mayb s u 1 por.ted in the frame I in any suitable manner, as bymeans of longl tudinal ribs on the interior surface of the frame, and it is preferably arranged to provide ventilating passages between the outside periphery of the stator core and the frame I. As shown in Fig. 1, the stator core 2 is disposed so that the ventilating passages 3. at the top of the frame r mu h smalle in a ha t e pa a at the lower side of the frame. This may be accomplished by mounting the core eccentrically in the frame I, or in any other desired manner. Suitable stator windings 5 of any desired type are placed in slots in the stator core 2. The frame. I: is closed by an end housing 6 of any suitable, type at the pinion end of the motor, and by. an. end housing 1: at the commutator end. The end hgusi ng s Qand I may be secured to the frame I in any desired manner, as by bolts 8.

The. shaft 9 of the motor is supported by roller bearings I0 and II in the end housings 6 and 1, respectively, and a rotor member i2 of any suitable type,'havi ng a laminated rotor core I3, is

securedrontheshait 9; A plurality of axialventilating passages Ill, eatend through the core i3,

. and a suitable. r tor winding I15 is: placed in slots in the periphery ofthe core l3 A commutator, e e all e i ia hi smeare n a mutator spid ounted on the shaft 9,, and a u it xi l vent latin assa extend r u he. qmmujtat r p r a of-the commutator 1.6 have necksor risers I9 at one end to which the rotor; wipding I5 is const rsg der dz in in h u a manner. Brushholders 20 forthebrushes; 2i. which engage the cornmutatari surface. are supported on a rocker ns n -Wm. which. nclu pp s d rocker ringsv 2?; connected: by.- axial bars 23.

Brush arms 214. are; secured tp the bars 23, and the brushholders 24}; are attached to the brush a s 4.. ,n Suitab e anner- An air inletopening; 2 5 is formed in the top part of the frame! at one end thereof directlyover the commutator, l5, Ventilating air is supplied; to the motor, through this inlet opening by means ofaduct 2.6;th1911 h which a high-veloc-.

ity streamof cool'airis forcedin any suitable manner, asbya blower on the locomotive. The air'fiowing through the. duct Z'Binto the inlet opening 251is dividedinto aplurality of streams by means of baflieszil'disposed in theinlet opening. These baflles-are, arranged-, as shown in Fig. 3, to-divide. the incoming airintoanumber of streams corresponding-to.themumber of spaces between,the..brushholders 25]: on the upper side of the commutator l6; and the baffles are shaped to effect a uniform and gradual change indirectionof the-ainflow. The-bafiles 21- extend entirely across thel inlet- 25: in the axial direction,

and thespacing between; the baffles is made such that thevelocity of -the air flowing into the motor through the'spaces between the baffles is the same as the velocity-of-theair in the duct 26.

Thus, the bafiles Zl-inefi ect forma plurality of nozzles through which highvelocity streams of cool air are directedin agenerally radial direction into the spaces be w'ee aie brushholders on the upper side; oi the commutator, as shown:

by the arrows in' The air directed agaihstthe upper side of the e nieio "i. n hi ma ner s. substantially prevented fron fiowing to, the lower. side of the commutator by means .of bafile.. .plates 28 on op-' posite sides of It 7 upper .part qi. .the.,space around. ,-the commutator from the lower part. Abouthali of the air flow oinmutator which divide the ing'through the'inlet opening 25 flows radially over the brushholders on the upper side of thecommutator and strikes the surface of the commutator at high velocity, thus having a very strong cooling effect. A part of this air, after striking the commutator, flows toward the end of the machine and into the ventilating passages l8 and I4 in the rotor through the relatively wide clearance 29 between the end of the commutator and the end housing I. The remainder of the air on the upper side of the commutator,"

after striking the commutator surface flows toward the opposite end of the machine, and-flows through the air gap and through the ventilating passage 3 between the stator core 2 and the frame I. The air flowing through both the rotor and stator passages escapes through discharge openings 30 at the pinion end. of the motor.

The rest of the air flowing through the inlet opening 25 from the duct 26, which does not strike the upper part of the commutator, flows past the brushholders and through corresponding openings 3| and 32 in the rocker ring 22 and end housing 1 into an air shield 33 which is secured to the outer surface of the end housing 1 in any suitable manner, as by screws 34. The air flowing into the air shield 33 in this manner,

as shown by the arrows in Fig, l, flows through the air shield which functions as a duct to'di-- rect the air to the opposite, or lower, side of the motor. At the lower side, the air flows through a plurality of openings 35 in the end housing- 1 back into the interior of the motor. Tubular members or'nozzles 36 are preferably placed in these openings to direct the air in generally axial'-' streams into the spaces between the brushhold-f ers 20 at the lower side of the commutator, and," if desired, wedge-shaped baflies 31may be placed give'the air a slight" in the tubular nozzles 36 to radial component.

commutator it flows into the air gap and into the relatively large passages 4 between the stator core 2 and the frame i, escaping through the discharge openings 36 at the opposite end of the ma- It will be noted that the clearance-be f tween the end of the commutator and the end chine.

housing I is made quite small at the lower side of the machine, and'since the nozzles 36 extend substantially past this clearance, practically none of "the air on the lower side flows into the rotor air passages.

A ring-shaped bafiie member 38 is preferably also provided between the rocker 'ring 22 and the stator core 2, as shown in Flg. l.' The baiile 3B is arranged so as to cause substantially fallpf" the air flowing-from, the commutator towards the stator air passages 3toflow directly across" the commutator bar necks l9. In this Way, the necks l9 and the soldered connections of, the winding to the commutator bars are prevent ed from becoming too hot, and softening of the solder and loosening of these connections in se rvice is prevented. The bafiie 38 may-extend all the way around the machine if desired but it is usually sufllcient for it to be placed only on the upper half of the machine, as shown in Fig. 1, since the commutatorrotates at high speed and Thus, the air flowing through the air shield 33 4 is directed in a plurality of generally aXiaL'hig'hvelocity streams into the spaces between the brushholders at the side of the commutator opposite to the air inlet 25. This air flows across the commutator surface and across the brush-- holders at high velocity so as to have a'very strong cooling effect, and after passing overtherelatively large size.

it is only necessary'for this cooling to be pro vided at one side.

- As previously described, the passages 3 between the stator core 2 and the frame I at the side of the machine adjacent the air inlet are made smaller than the corresponding passages 4 at the opposite side of the machine. The relatively small passages 3 result in a high back pressure tending to oppose the flow of air from the commutator, and this effect helps to force the air to flow through the clearance 29 and into and through the rotor air passages i 8 and I4, and into the air gap. It has been found that the air flowing at the back of the stator core in the passages.

3 has only a relatively slight cooling efiect, and the reduction of air flow through--these passages, therefore, has no material eifect on the temperature rise of the motor. Thus, the air directed against the upper side of the commutator is used to cool the rotor by flowing througlu the passages l8 and H, as well as to cool the stator;

windings and stator core.

The air diverted through the openings 32 and the air shield 33 is used only to cool the lower side of the commutator and the brushholders on that side, and the lower part of the stator core and windings. For this reason, the air shield 33 can be made relatively small in axial width since it needs to be only large enough to carry the re.-- quired volume of air for this purpose, and thus it can readily be made to fit into the available space. As previously indicated, the air passages 4 between the stator core and frame at the side opposite the air inlet opening 25 are made of. By making these passages relatively large, the back pressure is kept quite low, and the pressure difference across the commutator is kept high so as to maintain a highvelocity flow of air across the lower side of the commutator, and the brushholders on that side,

to obtain the maximum cooling efiect. Since all of the air passing across the lower side of the: commutator must escape through the stator airv passage 4, these air passages must necessarily be Y of relatively large size to provide an adequate area for the escape of the air without producing too high a back pressure which would tend to reduce the air velocity.

It should now be apparent that a ventilating system has been provided for electric motors of the commutator type which provides very effective. cooling of the commutator and the brushholders, which are the critical parts of the ma-.

subject to strict limitations.

system external tothe motor itself. By providing an air shield on the end of themotor which needs to be only large enough to carry halt.

of the ventilating air required for the motor, no change in size of the motor is required, but full advantage is taken of the available space. By using this air shield, the ventilating air is directed in axial streams into the spaces between the brushholders at the lower side of the com mutator, while air is directed in radial streamsinto the spaces between the brushholders at the, upperside of the commutator. In this way very "effective cooling-sv is obtainedsince no hot air pockets can exist between the brushholders, and higher horsepower ratings of the" motor:aire made possible without increase in the size or theimotor' than were obtainablewith' the'previ'ou'sly used:

constructions;

It is to be understoodithat although-a specifie embodiment of the invention has been: shown" and: described for the purpose? of illustratiom the invention is'capable of various other embodi ments and modifications; andii'n its broadest-as pects,it' includes: all equivalent constructions and' embodiments which: come within the scope of the appended claims.

' I claim as 'my invention:'

1 A dynamo-electric machine having: a: stator" member and a rotor member, a commutator on the rotor member; a plurality of brushholders supported on the stator member and spaced apart circumferential-1y around: the commutator; L inlet-means for' ventilating ai'r i'n the stator mem ber at one side of the commutator,means for dt recting a partof saidair in" a plurality of generally-radialistreams into the spaces between-the brushholders on the side of the commutator ad j'acent said inlet means, and means for directra-li-ty of' generally axial streams into the spaces between the brushholders on the other side of thecommutator;

iii A' dynamo-electric-machine having a stator member and a rotor member; a commutator-on the rotor member, a plurality of brushholders supported on the" stator member and spaced apart circumferentially around the commutator, inlet means for ventilating airin the stator memher" at one side of the commutator, meansror directing a part of said-air in a plurality of gen-- erallyradial streams into the spaces between thebrushholders' on the side of the commutator adjac'ent said inlet means; an air shield on the sta'- tor member adjacent the end of the'commutator, means for causinganother part of the ventilating' air to fiow into said air shield at the side of the commutator adjacentthe inlet'meansp theair shield extending to the other side'of the commutator, and means for directing theair from the air shield in a plurality of generally axial streams into the spaces between the brushholders on said other side of the commutator;

stator memberadjacent "the end of the airline-- tator, means for causing another part of" the? ventilating air to flow into-said airshield at the side of'the commutatoradjacent the inlet meansthe' air shield extending to the other side ofthe" 7 commutator," and means for directing the" air from the air shield' in a" plurality of gener'aliy axial streams into thespacesibetwe'en ithe brush-' holders on said oth'er side ofthe commutator;

in'g another part of the ventilating air in a plu' member andrai rotor member, said rotor'meinber including a: commutator and having passages for. ventilating air, said stator member.;;including a': frame and:- a stator 'core" supportedthe frame,-. 5? the" stator member also having p'a ssages for ventilating air, a plurality of brushholders sup ported on the stator member around the" com-.- mutatoninietmeans in the framez atone side" ofthecommutator for admitting airto'the ma If: chine; means for'substantially preventing direct, flow or air from one side'of the-commutator to;

the'other', means for directing apart of the-air irom itheinlet meansin a plurality of generally. radial streams'into't-he spaces between the brush-' l holders on theside or the commutator adjacent. the inlet' m'e'ans, said' air also flowing into the,

rotor air passages, and into the adjacent stator air passages, duct means for directing another partof the-"air from the inlet means to the opsposite -side or the commutator, and means for directing the air from said duct means in a phirality of generally axial streams" into the spaces.

between the brushholders on said opposite side ofthe commutator, said air flowing therefrom i into the adjacent stator air passages.

5; A dynamo-electric machine having a stator member and arotor member, said rotor member including a commutator, and having pas-1 sages for ventilating air, said-*stator'member in-iwcluding a frame and a stator core supported in the frame, the stator member also having. pas-1, sages for ventilating air, a plurality of brushholders supported onthe stator member around the commutatonbafile means extending at least. 5:; partway'around the machine between the brush-T holders and the stator core, inlet means in the frame at one side ,ofthe commutator fOI"admit ting air to the machine, means for substantially preventing direct flow of air from one side of the commutator to the other, means-for direct-- ing a'partoithe air from-theinliat means ina plurality of generally radial; streams into the' spaces between the brushholders .on the side of the commutator adjacent the inlet means, said- 45 air also flowing into the rotor air passages and into-the adjacent stator air passages, said baffle means causing ai-r flowing into the stator air passages toflow directly over the; end of the commutator, duct means for directing another 5: part of the air from the inlet means to-the: op-j posite side of the commutator anmmeans for directing the'air fromsaid duct means-in-a plurality of generally axial streams into the spaces between the brushholders-- on said opposite side ;,-.ofthe commutator, saidairflowing therefrom into the adjacent stator air passages;

6. A dynamo-electric machine having I a stator member and 1 arotor member, said-rotormemb erincluding a commutator and having passages for ,ventilatingair, said stator memberincluding: a

frame and 'astator core supported in the frame,

the stator member also having passages for ventilatingalrbetweenthe frame and thecore,

said passages-beingoi relativelylarge size at one side of the machine andbeing ofrelatively smallersizeat the othersideof the-machinea plurality of-brushholders supported on the stator member around'the-commutator, inlet means for ventilating air in the frame-adjacent'the com mutator; said inlet means beingoathe same side of'theframe'asthe smaller air passages, means for substantially preventing direct flow of--- air from one 'sideof i the commutator to the other,

means' ior' directing a part of the air from the 4: a dynamo-electric machine liavingizwstator 15; inletmeans-in a plurelity ofgenerally radial,-

streams into the spaces between the brushholders on the side of the commutator adjacent the inlet means, said air also flowing into the rotor air passages and into the adjacent stator air passages, duct means for directing another part of the air from the inlet means to the opposite side of the commutator, and means for directing the air from said duct means in a plurality of generally axial streams into the spaces between the brushholders on said opposite side of the commutator, said air flowing therefrom into the adjacent stator air passages.

7. A dynamo-electric machine having a stator member and a rotor member, said rotor member including a commutator and having passages for ventilating air, said stator member including a frame and a stator core supported in the frame, the stator member also having passages for ventilating air, an end housing closing the end of the frame adjacent the commutator, a plurality of brushholders supported on the stator member around the commutator, inlet means in the frame at one side of the commutator for admitting air to the machine, means for substantially preventing direct fiow of air from one side of the commutator to the other, means for directing 'a part of the air from the inlet means in a plurality of generally radial streams into the spaces between the brushholders on the side of the commutator adjacent the inlet means, said air also flowing into the rotor air passages and into the adjacent stator air passages, an air shield on the outside of said end housing, said end housing having openings adjacent the inlet means permitting another part of the air from the inlet means to flow into the air shield, and means at the opposite side of the end housing for directing the air from the air shield in a plurality of generally axial streams into the spaces between the brushholders on the side of the commutator opposite the inlet means, said air flowing therefrom into the adjacent stator air passages.

8. A dynamo-electric machine having a stator member and a rotor member, said rotor member including a, commutator and having passages for ventilating air, said stator member including a frame and a, stator core supported in the frame, the stator member also having passages for ventilating air, an end housing closing the end of the frame adjacent the commutator, a plurality of brushholders supported on the stator member around the commutator, inlet means in the frame at one side of the commutator for admitting air to the machine, means for substantially preventing direct flow of air from one side of the commutator to the other, means for directing a part of the air from the inlet means in a plurality of generally radial streams into the spaces between the brushholders on the side of the commutator adjacent the inlet means, said air also flowing into the rotor air passages and into the adjacent stator air passages, an air shield on the outside of said end housing, said end housing having openings adjacent the inlet means permitting another part of the air from the inlet means to flow into the air shield, and a plurality of tubular members extending through the end housing into the air shield at the opposite side of the end housing, said tubular members directing the air from the air shield in a plurality of generally axial streams into the spaces between the brushholders on the side of the commutator opposite the inlet means, said air flowing therefrom into the adjacent stator air passages.

9. A dynamo-electric machine having a stator member and a rotormember, said rotor member including a commutator and having passages for ventilating air, said stator member including a frame and a stator core supported in the frame, the stator member also having passages for ventilating air between the frame and the core, said passages being of relatively large size at one side of the machine and being of relatively smaller size at the other side of the machine, an end housing closing the end of the frame adjacent the commutator, a plurality of brushholders supported on the stator member around the commutator, inlet means for ventilating air in the frame adjacent the commutator, said inlet means being on the same side of the frame as the smaller air passages, means for substantially preventing direct flow of air from one side of the commutator to the other, means for directing a part of the air from the inlet means in a plurality of generally radial streams into the spaces between the brushholders on the side of the commutator adjacent the inlet means, said air also flowing into the rotor air passages and into the adjacent stator air passages, an air shield on the outside of said end housing, said end housing having openings adjacent the inlet means permitting another part of the air from the inlet means to flow into the air shield, and a plurality of tubular members extending through the end housing into the air shield at the opposite side of the end housing, said tubular members directing the air from the air shield in a plurality of generally axial streamsinto the spaces between the brushholders on the side of the commutator opposite the inlet means, said air flowing therefrom into the adjacent stator air passages.

ERICH O. MUELLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,525,691 Poth Feb. 10, 1925 1,784,102 Lincoln Dec. 9, 1930 920,725 Callan May 4, 1909 1,883,288 Zubaty Oct. 18, 1932 2,315,177 Zadnik Mar. 30, 1943 

